Blown films are produced by forming a cylindrical bubble from molten polymer materials, then cooling and splitting the cylindrical bubble to form the blown film. The process is continuous, so the blown film forms long continuous sheets which can be rolled for transport and storage. The blown film can be fabricated into items such as carrier bags, food packaging, stand up pouches, and label films.
Increasing environmental awareness on the part of consumers has led to an increasing demand for biopolymer blown films, i.e., films made from renewable resources which are biodegradable such as polylactic acid (PLA) and the like. Unfortunately, biopolymers are difficult to handle when forming the blown film. Biopolymers are stiff and brittle, with poor elongation properties, resulting in low bubble strength and bubble tears. For example, blown films made of greater than 95 percent PLA typically have elongation-at-break values under 20 percent. Further, the blown films wrinkle and tear easily during handling after the bubble has been collapsed into the blown film so that the blown film breaks when being wound into rolls. Such problems increase costs through lost production and lost materials, preventing efficient biopolymer film production on blown film lines.
It would be desirable to have a biopolymer blown film extrusion system and method that would overcome the above disadvantages.